It has been known that a conductive polythienyl can be formed by the electrolytic polymerization of a thienyl derivative. This conductive polythienyl has been applied to electronic devices such as diodes and field effect transistors, and to optoelectronic devices including electrochromic elements, optical memory elements and the like. Due to the recent miniaturization of devices, conductive films are consequently required to be made thinner. It has also been a goal to develop a thienyl derivative which can form a conductive ultrathin film much more easily and consistently than other materials.
Forming a conductive ultrathin film on a substrate surface by using a thienyl derivative can be done by the following procedure:
providing a monomer by bonding long-chain organic groups to thienyl; PA1 forming a monomer monomolecular film on a substrate surface by the Langmuir-Blodgett method (LB method); and PA1 polymerizing the film on the substrate surface. PA1 (wherein X.sup.1, X.sup.2 and X.sup.3 are the same or different and represent a halogen atom or an alkoxy group with 1-4 carbon atoms).
However, in case of this conventional thienyl derivative, the monomolecular film is only physically adsorbed to the substrate even by the LB method. The monomer is also likely to be evaporated or scattered before or during the polymerization process. Therefore, it has been difficult to form a fully optimal conductive ultrathin film.